Every person has a unique way of speaking, called an idiot. The language used by a group of speakers is its dialect. The dialects of a language are the mutually intelligible forms of the language that differ in systematic ways form each other. Dialects develop because language change and the changes that occur in one group or area may differ from those that occur in another. Regional dialects and social dialects develop for this reason.

The attempt to understand what makes language acquisition and use possible has led to research on the brain- mind-language relationship. Neurolinguistics studies the brain mechanisms and anatomical structures that underlie linguistic competence and performance, and how they developed over time.

The brain is the most complicated organ of the body, controlling motor and sensory activities and thought processes. Research conducted for over a century reveals that different parts of the brain are called the cortex, which serves as the initiating all voluntary actions The brain of all higher animals is divided into two parts called the cerebral hemispheres, which are connected by the corpus Callosum , a pathway that permits the left and right hemispheres to communicate.

Although each hemisphere appears to be a mirror image of the other, they exhibit

Contralateral control of functions. The heft hemisphere controls the right side of the body and the right hemisphere controls the heft side. Despite the general symmetry of the human body. There is much evidence that the brain is asymmetric,with the left and right hemispheres specialized for different functions.

Evidence from studies of aphasia- language dysfunction as a result of brain in juries and from surgical removal of parts of the brain , electrical stimulation studies, emission tomography results removal of parts of the brain electrical stimulation studies, emission tomography results, dichotic listening and experiments that measure brain electrical activity , show a lack of symmetry of function of the two hemispheres these results are supported by studies of split- brain patients, who, for medical reasons, have had the corpus callosum severed in the past, the studies of the brain and language depended on surgery or autopsy. Today, technologies such as magnetic resonance imaging(MRI) and positron- emission tomography (PET) make it possible to see the sites of lesions in the living brain, to detect changes in brain activities, and to relate these changes to localized brain damage and cognitive tasks.

For normal right-handers and many left-handers, the left side of the brain id specialized for language. Thislateralization of functions id genetically and neurologically conditioned Lateralization refers to any cognitive functions that are primarily localized to one side of the brain or the other.

In addition to aphasia, other evidence supports the lateralization of language. Children with early brain lesions in the heft hemisphere resulting in the surgical removal of part or all of the heft brain show specific linguistic deficits, while other cognitive abilities remain intact. If the right brain is damaged, however, language is unimpaired but other cognitive disorders may result.

Aphasia studies show impairment of different parts of the grammar. Patients with Broca'saphasia exhibit impaired syntax and speech problems. Patients with Wernicke's aphasia are fluent speakers who produce semantically empty utterances and have difficulty in comprehension. Anomia is a form of aphasia in which the patient has word finding difficulties. Patients with jargon aphasia may substitute words unrelated semantically to their untended messages; others produce phonemic substitution errors, sometimes resulting in nonsense forms that make their utterances uninterpretable .

The language faculty is modular. It is independent from other cognitive systems with which it interacts. Evidence for modularity is found in studies of aphasia, of children with specific Language Impairment (SLI), and of savants. Children with SLI suffer from language deficits, but are normal in other regards. Language savants are individuals with extraordinary Language skills, but who are deficient in general intelligence. Their existence suggests that linguistic ability is not derived from some general cognitive ability, but exists that independently.

The genetic basis for an independent language module is supported by studies of SLI in families and twins.

The critical-age hypothesis states that there is a window of opportunity between birth and puberty for learning a first language. The imperfect language learning of persons exposed to language after this period supports the hypothesis. Some songbirds also appear to have a critical for the acquisition of their calls and songs. The origin of language in the species has been a topic for much species has been a topic for much speculation through out history. The idea that language was God's gift to humanity is present in religions throughout the world. The continuing belief in the miraculous powers of language is tied to this notion. The assumption of the divine origin of language stimulated interest in discovering the first primeval language. There are legendary experiments in which children were isolated in the belief that their first words would reveal the original language.

Other views suggest that language is a human invention, stemming from "cries of nature," early gestures, onomatopoeic words, or even from songs to express love. The ancient Greeks believed that a "legislator " gave the true names to all things.

Language most likely evolved with the human species, possibly in stages, possibly in one giant leap. Research by linguists, evolutionary biologists, and neurologists support this view, and the view that from the outset the human animal was genetically equipped to learn language. Studies of the evolutionary development of the brain provide some evidence for physiological and anatomic preconditions for language development.